This invention relates to a wheel bearing assembly for rotatably supporting a vehicle wheel relative to a vehicle body, and more particularly to a wheel bearing assembly comprising a hub ring, an outer member of a constant-velocity joint and a double-row wheel bearing in a modular form.
A conventional wheel bearing assembly shown in FIG. 17 includes an outer member 1, an inner member 2, an inner ring 3 and rolling elements 4 arranged in two rows. The inner member 2 has at its outboard end a radially outwardly extending flange 5 for mounting a vehicle wheel, and is formed with a first raceway 6a on its radially outer surface. The inner ring 3 is pressed on a cut-out, small-diameter cylindrical portion 7 of the inner member 2 at its inboard end. It is formed with a second raceway 6b on its radially outer surface.
The outer member 1 is formed with first and second raceways 8a, 8b on its radially inner surface, opposite the first and second raceways 6a, 6b, respectively. The rolling elements 4 are mounted between opposed pairs of the raceways. The outer member 1 has on its radially outer surface a flange 9 adapted to be fastened to an unillustrated vehicle suspension.
The inner member 2 is coupled to an outer member 11 of a constant-velocity joint (CVJ) 10. The CVJ outer member 11 comprises a cup 12 and a stem 13. The stem is inserted into and coupled to the inner member 2 by serrations with its threaded end 14 protruding from the outboard end of the inner member. A nut 15 is threaded onto the threaded end 14 of the stem 13 and tightened to press the inner member 2 against a shoulder 16 with the inner member 2 and the inner ring 3 axially positioned relative to each other, thereby applying a preload to the rolling elements 4. The rolling elements each have a contact angle. The abovesaid preload increases the bearing rigidity and allows the rolling elements to bear a moment load.
In the arrangement of FIG. 18 (disclosed in Japanese patent publication 10-297208), the inner member 2 is coupled to the stem 13 of the CVJ outer member 11 by serrations 17. The inner ring 3 is pressed both on the inner member 2 and the CVJ outer member 11 and coupled thereto by serrations 18. Since the CVJ outer member 11 is coupled to the bearing assembly through both the serrations 17 and 18, a larger torque can be transmitted between the CVJ and the bearing assembly than in the arrangement of FIG. 17.
In this arrangement, because the inner ring 3 is partially pressed on the CVJ outer member 11, the axial length of the bearing assembly is relatively short. But since the CVJ outer member has to be coupled to the bearing through the radially spaced two different sets of serrations, it is troublesome to assemble such a bearing assembly.
A first object of the present invention is to provide a wheel bearing assembly that is compact, lightweight and easy to assemble.
FIG. 19A shows another conventional wheel bearing assembly, which comprises an outer member 1 into which is pressed an outer ring 19 formed with two annular raceways on its radially inner surface, and an inner member 2 onto which are pressed two separate inner rings 3 formed with raceways 6a, 6b on the respective radially outer surfaces thereof, opposite the raceways 8a, 8b. Rolling elements 4 are disposed between the two opposed pairs of raceways. The inner member 2 has a flange to which is adapted to be mounted a vehicle wheel.
A stem 13 of an outer member 11 of a constant-velocity joint (CVJ) 10 is inserted into a serrated bore 20 of the inner member 2 with its threaded free end protruding into a pilot portion 21 of the flange 5. A nut 22 is threaded onto the threaded end of the stem 13 to fasten the CVJ outer member 11 to the inner member 2.
Contrary to a wheel bearing assembly for supporting a driving wheel, a typical bearing assembly for supporting a non-driving wheel has its outer member mounted to the wheel through its flange and its inner member directly secured to the end of a stationary axle.
The wheel bearing assembly is fastened to the stationary axle or to the wheel drive shaft by e.g. threading a bolt having a polygonal head or a head with a polygonal hole into the end of the stationary shaft or the wheel drive shaft.
Such a bolt or nut tends to loosen due e.g. to vibration of the vehicle. Thus, it is desired to provide such a bolt or nut with a means for preventing it from loosening various means for preventing loosening of a nut such as the nut shown in FIG. 19A are known. For example, in the arrangement of FIG. 19B, the nut is prevented from loosing by pressing a snap ring 23 into a cutout 13a formed in the stem 13 near its tip by deforming (e.g. caulking) the ring 23. Also, a pin may be inserted into the stem to prevent loosening of the nut. A double-nut arrangement is another well-known means for preventing loosening.
But there is not known any means for preventing loosening of a bolt threaded into a shaft.
A second object of the present invention is to provide a wheel bearing assembly having a means for preventing loosening of a nut threaded onto a shaft or a bolt threaded into the shaft to fasten the shaft to the bearing.
FIG. 20 shows another conventional bearing assembly for a driving wheel, comprising the bearing assembly of FIG. 17 with a constant-velocity joint 10 including an outer member 11 and an inner ring 29, a brake rotor 24 and a knuckle 25 assembled together in a modular form.
A pulser ring 26 for ABS is mounted on the outer surface of the cup 12 of the CVJ outer member 11. A sensor (not shown) is mounted on a vehicle body (not shown either), opposite the pulser ring 26.
The brake rotor 24 is mounted on a flange 5 of the inner member 2 by bolts 31. The knuckle 25 is mounted to the flange 9 of the outer member 1 by bolts 27.
The bearing gap defined between the inner member 2 and the outer member 1 has its outboard and inboard ends sealed by seals 28a and 28b, respectively. Rolling elements 4 are disposed in the bearing gap.
Since the inner ring 3 is pressed onto the inner member 2 and not onto the CVJ outer member 11. Thus, even when the latter is pulled out of the inner member 2 for maintenance, the inner ring 3 will remain coupled to the inner member 2.
Such the bearing assembly tends to be heavy because it includes many heavy parts. A lightweight bearing assembly is therefore desired. Also in these conventional arrangements, the gap between the seal 28a and the outboard rolling elements 4, the gap between the outboard and inboard rolling elements 4, and the gap between the seal 28b and the inboard rolling elements 4 are too small to mount the pulser ring 26 and a sensor therein.
A third object of the invention is to provide a wheel bearing assembly that is lightweight, has a sufficiently large closed space in which a pulser ring and a sensor can be mounted, and can form a bearing assembly together with other parts.
According to this invention, in order to attain the first object, there is provided a wheel bearing assembly comprising an outer member having a flange adapted to be mounted to a vehicle body and formed with first and second raceways on inner surface thereof, an inner member having a flange on which a vehicle wheel is adapted to be mounted and formed with a first raceway on outer surface thereof, an inner ring formed with a second raceway on outer surface thereof, a plurality of rolling elements disposed between the raceways on the outer member and the first and second raceways, a constant-velocity joint having an outer member comprising a cup portion and a stem portion, the stem portion engaging the inner member through mesh engagement, the inner ring being mounted on the outer member of the constant-velocity joint with its outboard end abutting an inboard end of the inner member.
The inner ring may be coupled to the CVJ outer member by pressing the former onto the latter. The engagement means may comprise splines, serrations or keys.
In the prior art arrangement of FIG. 17 or 18, since the inner ring is pressed onto the inner member, the inner member inevitably has a small inner diameter than the inner ring. In the arrangement of this invention, since the inner ring is pressed onto the CVJ outer member with its outboard end abutting the inboard end of the inner member, it is possible to reduce the thickness of the inner member and thus increase the outer diameter of the stem and thus the serrations thereon. This makes it possible to reduce the axial length of serrations and thus the axial length of the entire bearing assembly. Also, because a greater strength is assured with a larger-diameter stem, it is possible to use a hollow and thus lightweight stem. Since the inner member is also thin and thus lightweight, the entire assembly is lightweight. Since the CVJ outer member is coupled to the inner member by serrations at a single location, the bearing assembly of this invention can be assembled more easily than the arrangement of FIG. 18.
The inner ring is secured onto the CVJ outer member instead of being butted against the shoulder of the CVJ outer member. Thus, the bearing assembly of this invention may have a smaller axial length than the bearing assembly of FIG. 17. To reduce the axial length of the bearing assembly, the inboard raceway may directly formed on the shoulder of the CVJ outer ring while omitting the inner ring. (This arrangement is not shown.)
But the CVJ outer member is ordinarily formed by induction-hardening carbon steel for machine parts such as S53C. An inboard raceway formed directly on such an induction-hardened CVJ outer member tends to be lower in hardness than a raceway formed by carburizing or hardening. A separate inner ring can be hardened, so that a harder and more durable raceway can be formed thereon. The inner ring may be formed from medium- to high-carbon steel, which can be hardened and is high in wear resistance, elastic limit and fatigue resistance.
By deforming the outboard end of the stem and engaging it against the end face of the inner member, it is possible to reliably prevent the inner member from coming out of the CVJ outer member. Also, since no nut is used, it is possible to reduce the number of parts and thus to reduce the weight of the assembly.
If the inner diameter of the inner member, especially at its end near the inner ring, is smaller than the inner diameter of the inner ring, the CVJ outer member can be easily pressed into the inner ring.
The stem portion is preferably hollow for reduced weight.
The cup portion of the CVJ outer member has a flat inner bottom. A jig is pressed against this flat bottom when the distal end of the stem is deformed or when the CVJ outer member is pressed into the inner ring to bear an axial load.
In order to attain the second object, according to the present invention, there is provided a wheel bearing assembly comprising an outer member having a flange adapted to be mounted to a vehicle body and formed with two raceways on inner surface thereof, an inner member having a flange on which a vehicle wheel is adapted to be mounted and formed with a first raceway on outer surface thereof, an inner ring formed with a second raceway on outer surface thereof, a plurality of rolling elements disposed between the raceways on the outer member and the first and second raceways, a constant-velocity joint having an outer member comprising a cup portion and a stem portion, the stem portion mounted in and engaging the inner member through mesh engagement, the flange of the inner member having a pilot portion at its outboard end, the stem portion having its outboard end inserted into and fastened to the inner member at the pilot portion by means of a fastener such as a nut and a bolt, a cap inserted into the pilot portion around the fastener, a first engaging means for engaging the fastener with the cap, and a second engaging means for engaging the cap with the pilot portion, whereby preventing the fastener from loosening.
The cap inserted into the pilot portion prevents the bolt or nut from turning in the loosening direction relative to the cap, and the cap is prevented from turning in the loosening direction relative to the pilot portion. Thus, the bolt or nut cannot turn in the loosening direction relative to the pilot portion.
The first engaging means may comprise an inner wall provided integrally with the cap inside of the cap, the fastener having a polygonal portion, the inner wall having a plurality of recesses arranged circumferentially so as to receive corners of the polygonal portion of the fastener. This allows the cap to a desired position and allows the fastener to be clamped at a suitable position.
The second engaging means may comprise at least one recess provided on one of the inner wall of the pilot portion and the cap, and at least one protrusion provided on the other so as to be received in the recess, whereby preventing the cap from loosening.
An arrangement for preventing the cap from coming out of the pilot portion is provided. The arrangement may comprise an annular groove formed in the inner wall of the pilot portion, and a circumferential rib formed on the outer surface of the cap so as to be pushed into the annular groove by caulking.
In order to attain the third object, according to the present invention, there is provided a wheel bearing assembly comprising an outer member having a flange adapted to be mounted to a vehicle body and formed with two raceways on inner surface thereof, an inner member having a flange on which a vehicle wheel is adapted to be mounted and formed with a first raceway on outer surface thereof, an inner ring formed with a second raceway on outer surface thereof, a plurality of rolling elements disposed between the raceways on the outer member and the first and second raceways, a constant-velocity joint having an outer member comprising a cup portion and a stem portion, the stem portion mounted in and engaging the inner member through mesh engagement, and a coupling member for coupling the inner member and the inner ring together with an inboard end of the inner member abutting an outboard end of the inner ring.
The inner ring may comprise an outboard inner ring and an inboard inner ring with the outboard end of the former inner ring abutting the inboard end of the inner member. In this arrangement, the coupling member couples the outboard inner ring and the inboard inner ring together.
The coupling member may comprise an annular member with or without a cutout, the annular member comprising an annular base, and a pair of flanges extending radially outwardly from side edges of the annular base and engaged in the annular grooves formed in the inner member and the inner ring or in the inboard and outboard inner rings near their abutting ends, respectively.
The engaging means formed on the bore of the inner member and the stem portion may comprise serrations. The serrations on the bore of the inner member may engage the serrations on the stem portion with a preload and the stem portion may be pressed into the inner ring with a predetermined interference.
The annular grooves should be provided inboard of the serrations. The stem portion may be hollow. The stem portion may be fastened to the inner member by a bolt threaded into the stem portion.
The cup portion is formed with a seal land on its outer surface, and the bearing assembly may further comprise a seal kept in sliding contact with the seal land, and a pulser ring mounted between the seal land and the rolling elements disposed between the inboard raceways.
A knuckle is mounted on the flange of the outer member, and a sensor is mounted to a radially inner surface of the knuckle, radially opposite the pulser ring, and the seal is mounted on the sensor. This arrangement improves the reliability of speed detection for ABS.